[333pg333]

Can those that have upgraded from the Mo30 S4 or 968cs brakes to for example the

Big Red/Black or anything else please comment on what your impressions are and if you would go the trouble and expense if you had your time over. There seems to be varying opinions from "Don't bother, the Mo30's are plenty big enough" to " I couldn't believe the difference and would recommend them highly". Specifically with track work in mind as that's where you find out what's what.

Thanks

Partial Post: Please Login or Register to read the full post.

[Anchorman]

I haven't upgraded, but the one comment I would offer is this. I've now ridden in a number of Porsches at Watkins Glen. In every case where I asked what they did to the brakes - because they seemed to have pretty awesome stopping power - the answer was consistently "Nothing - the brakes are stock." These were not cars with stock Big Reds or Big Blacks.

Partial Post: Please Login or Register to read the full post.

[Dave]

Can't comment on Big Reds and such, but the M030 calipers I added along with the stainless brake lines and good pads = fade-free braking now through many a track day, a handful of sprint races, and an two enduro's.



The real test will be the 90-minute enduro at Road America in a few weeks, but I'm feeling pretty good about it right now <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />

Partial Post: Please Login or Register to read the full post.

[sasilverbullet]

I second Dave's motion - stainless lines, fresh brake fluid and some good pads...awesome winning combination!

Partial Post: Please Login or Register to read the full post.

[333pg333]

This is what I have got. S4 Mo30 brakes, s/s braided lines, ebc yellows f greens r, Caltex $$$ race brake fluid, 968cs underbody air deflectors and have been bled many times. I am still feeling like the other, more modern P-cars seem to brake for much less time and look more balanced. I also have Mo30 suspension and stiffer springs w uprated valving in front Koni's so it's not bog standard. Maybe I'm just coming in to some corners too hot? Getting new suspension which should have less dive and squat maybe this will help?

Partial Post: Please Login or Register to read the full post.

[TheMirror]

Are you still using the standard brake proportioning valve? If so, your brakes may be too biased towards the front. Some people on the boards here have changed their proportioning valve for more rear braking.



http://www.968forums.com/index.php?showtop...ortioning+valve

Partial Post: Please Login or Register to read the full post.

[333pg333]

As far as I know it's the standard valve. I haven't had any problems as far as locking up. ABS sees to that. What would changing the proportioning do as far as reducing the braking time be though I wonder?

Partial Post: Please Login or Register to read the full post.

[TheMirror]

From what I understand from other posts (and in theory), is shifting a greater percentage of braking back towards the rear wheels will see them do more of the work. Its a delicate balance in non-ABS cars, because the last thing you want on the racetrack is rear wheel lockup. With ABS, you can push it a little more.



With a lowered car and stiffer suspension, the center of gravity is lower and may (not sure) shift rearward somewhat. Certainly under maximum braking the center of gravity will be further rearward. Thus, using a proportioning valve that biases braking a little more towards the rear will take some of the load off of the fronts.....and make all 4 more effective.



Thoughts from those with more experience than I?



-Mirror

Partial Post: Please Login or Register to read the full post.

[Dave]

I did forget to mention that I do have the proportioning valve in there too. Be sure to bleed the ABS (need to engage it after the change, then re-bleed system - wet road is handy for this) after changing the valve.



Not sure it makes that big of a difference, given the ABS.



Stability under braking in these cars seems to be a function of the following:



- Tire size / diameter / correct pressures

- Alignment (can make that rear end feel "spooky")

- Pads - I don't have experience with the pads you mention



Sounds like you are adjusting brake bias with the running of different pads F/R already.



In any case, you should be able to out-brake the non-ABS 911's (3.2 Carreras) even though they are significantly lighter cars. If you're able to light-up the ABS under braking and particularly while trail-braking into the turns... the brakes are fine.



Hell, I wouldn't have added all the bloody unsprung weight of those M030 calipers and rotors if I didn't spend the second 45 minutes of an enduro having to use 2 feet and a prayer to brake for T5 at RA!



That said, Big Reds only seem to add about a pound per corner over the M030's and will remove all question about having enough brake <img src="/forum/images/smilies/968/wink.gif" class="smilie" alt="" />

Partial Post: Please Login or Register to read the full post.

[Anchorman]

Mirror: you wrote "...under maximum braking the center of gravity will be further rearward." Huh? My physics lessons taught me the opposite. When braking (whether maximum or otherwise), the vehicle's weight is shifting forward, not rearward. In fact, that's one of the reasons that trail braking is such an art - you're asking the front wheels to do double-duty - turn while under the extra load from the weight shift induced by braking. And that's why us novices (definitely me included) don't do it - we brake and then turn.

Partial Post: Please Login or Register to read the full post.

[flash]

i think he means that because of the stiffer suspension, less weight shift is at the front - this is also the case in my car - my brake balance got a lot better when i increased my spring rates



as example of the ease of change to the balance, in the denali, i just dropped the rear suspension height another inch, and the rear brakes are now so MUCH more efffective, and it brakes so flatly, that i have to adjust the trailer brakes down, or they will lock up

Partial Post: Please Login or Register to read the full post.

[wjk_glynn]

[quote name='Anchorman' date='Aug 8 2006, 06:24 PM']Mirror: you wrote "...under maximum braking the center of gravity will be further rearward."  Huh?  My physics lessons taught me the opposite.  When braking (whether maximum or otherwise), the vehicle's weight is shifting forward, not rearward.  In fact, that's one of the reasons that trail braking is such an art - you're asking the front wheels to do double-duty - turn while under the extra load from the weight shift induced by braking.  And that's why us novices (definitely me included) don't do it - we brake and then turn.

[right][post="25112"]<{POST_SNAPBACK}>[/post][/right][/quote]



I think Mirror intended to say that a lowered car would have its center of gravity shifted towards the rear ("With a lowered car and stiffer suspension, the center of gravity is lower and may (not sure) shift rearward somewhat") - and not that the act of braking shifts weight towards the rear.



But having said that...



Lowering a car equally at the front and rear will not move the center of gravity back or forth (relative to the contact patches) significantly unless there is some horrible suspension geometery in the car (that litteraly causes the car's tires to move longtitudely).



Where the benefit of lowering a car comes into play is that it has (an obvious) effect of lowering the height of the center of gravity.



When you lower the height of the center of gravity, the effective grip of the tires increases because of the change in angle at which the center of gravity acts through the tires' contact point. You can achieve the same effect with lateral grip if you increase the track-width of the car, or traction/braking if you lengthen the wheel base of the car.



So when you increase the effective grip of the tires (and specifically the grip at the rear in this case), you can run more rear brake bias before you get lockup.



Another trick is to change the rake of the car - i.e. lower the rear a little more than the front so the car has a slightly pitchup attitiude. This techinque was used in the Turbo Cup series to tune the front-to-rear balance of the car (along with sway bar settings).



Karl.

Partial Post: Please Login or Register to read the full post.

[333pg333]

I think the main reason is that I'm coming in to the corners pretty hard and maybe carrying a little too much speed combined with the softer (than I'm upgrading to) springs/shocks which is causing me to pitch forward and having to really stand on the pedal. This causes me to spend too much time settling the car into the turn. Also I'm finding especially on tighter turns it's taking me too much time through the turn until I'm able to apply power due to loss of traction so perhaps I'm slowing down more than I would need given a suspension setup that allows me to power out of the turn earlier? Also bear in mind that I'm in a 944 turbo 's' which is chipped, has a dual port wastegate, and runs about 1.3 bar which is probably good for about 280-300hp at the crank. Also I'm not undertyred as I was on brand new 255/35 f and 285/30 r 18" r-spec Toyo R888's so plenty of grip! I can make the whole process much smoother by turning down the boost which makes you slower (terminal speed)and neater, but maybe just as fast lap times?

Also can someone give a brief explanation of 'Trail Braking' please? My impression is that you brake actually later while turning before getting on the gas pedal? As opposed to brake then turn.

I wonder when you upgrade calipers, rotors, pads etc...but the other parts of your brake system stays stock such as master cylinder and booster, is it possible to upgrade these components. Surely GT3's or whatever, have bigger more efficient versions of these? Is this an oversimplification? It's just that they seem to just touch the brakes for far less time when I'm doing a Fred Flintsone impersonation and feel like my feet are about to go through the firewall.

Partial Post: Please Login or Register to read the full post.

[sparky]

Speaking from direct experience tracking my 968CS at Mallala, reputedly the hardest circuit on brakes in Australia (three hairpins).... you simply don't need to go bigger than M030 size brakes on a 968. In fact you'll go backwards due to the increase in unsprung weight affecting your acceleration and grip on bumpy surfaces.



By comparison a mate's stock 968 with non-M030 brakes pulled up just as well on track, but only for about 4 laps, then they started to overheat. So M030's don't make you stop harder, they stop just as hard but for much longer, due to their extra mass and cooling ability to handle the heat caused by over 1000bhp of brake power ;-)



in summary ... my M030 discs with Ferodo DS2500 pads *never* fade... fantastic.

Partial Post: Please Login or Register to read the full post.

[flash]

i found the same thing at PIR friday - i had plenty of brakes in nearly stock layout - i didn't like the balance, and will correct that, but stopping was not a problem, and no fade whatsoever

Partial Post: Please Login or Register to read the full post.